1// SPDX-License-Identifier: GPL-2.0-only
2/* Timeout API for single-threaded programs that use blocking
3 * syscalls (read/write/send/recv/connect/accept).
4 *
5 * Copyright (C) 2017 Red Hat, Inc.
6 *
7 * Author: Stefan Hajnoczi <stefanha@redhat.com>
8 */
9
10/* Use the following pattern:
11 *
12 *   timeout_begin(TIMEOUT);
13 *   do {
14 *       ret = accept(...);
15 *       timeout_check("accept");
16 *   } while (ret < 0 && ret == EINTR);
17 *   timeout_end();
18 */
19
20#include <stdlib.h>
21#include <stdbool.h>
22#include <unistd.h>
23#include <stdio.h>
24#include "timeout.h"
25
26static volatile bool timeout;
27
28/* SIGALRM handler function.  Do not use sleep(2), alarm(2), or
29 * setitimer(2) while using this API - they may interfere with each
30 * other.
31 */
32void sigalrm(int signo)
33{
34	timeout = true;
35}
36
37/* Start a timeout.  Call timeout_check() to verify that the timeout hasn't
38 * expired.  timeout_end() must be called to stop the timeout.  Timeouts cannot
39 * be nested.
40 */
41void timeout_begin(unsigned int seconds)
42{
43	alarm(seconds);
44}
45
46/* Exit with an error message if the timeout has expired */
47void timeout_check(const char *operation)
48{
49	if (timeout) {
50		fprintf(stderr, "%s timed out\n", operation);
51		exit(EXIT_FAILURE);
52	}
53}
54
55/* Stop a timeout */
56void timeout_end(void)
57{
58	alarm(0);
59	timeout = false;
60}
61